[62525] Non-working days can be choosen via date field

[HDinger]

Ticket

https://community.openproject.org/projects/openproject/work_packages/62525/activity

What are you trying to accomplish?

Show an error message when the user manually enters a non-working day

Screenshots

What approach did you choose and why?

The SetAttributesService silently shifts dates to the next possible date if a non-working day is entered. This makes absolutely sense for the Gantt view but in the datepicker we want some kind of feedback and prevent that shift.